A method for growing and evaluating electro-optic properties of an electro-optic crystal Bi2WO6

Abstract

This invention discloses a growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic properties. Raw materials are weighed according to a molar ratio of Bi2O3:WO3 = 1:1, and Bi2WO6 powder is synthesized using a solid-state method. The powder is pressed into sheet samples for infrared and Raman spectroscopy testing. Infrared oscillation intensity data is extracted from the infrared spectrum, and average Raman scattering efficiency data is extracted from the Raman spectrum. The contribution of ion motion is extracted based on peaks in the same wavelength band in the data. g l The second harmonic generation (SHG) coefficient of Bi2WO6 powder was measured, and the electron motion contribution was extracted from the SHG coefficient measurement data. g e ; Contribution of ion motion g l and electron motion contribution g e The electro-optic coefficient was finally calculated. The powder was mixed with a flux and placed in a platinum crucible, which was then placed in a molten salt growth furnace and heated to form a homogeneous melt. A cooling program was set, and the mixture was rapidly annealed after cooling to room temperature to remove the flux, finally yielding Bi2WO6 crystals. Using powder for electro-optic coefficient calculation reduces computational and experimental costs.

Description

Technical Field

[0001] This invention belongs to the field of electro-optic materials technology, specifically, it relates to a growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic properties. Background Technology

[0002] Electro-optic crystals are core optoelectronic functional materials for laser modulation, optical switching, and information processing, playing a crucial role in optical communication and ultrafast laser technologies. With the increasing integration of optoelectronic devices, the market demand for novel materials possessing high electro-optic coefficients, wide transparency bands, and high physicochemical stability is becoming increasingly urgent. Bi₂WO₆ is a representative example. d 0 Transition metal oxides, with their unique layered structure and [WO6] octahedral distortion, exhibit significant ion shift contributions and excellent physicochemical stability, making them an important direction for developing high-performance electro-optic materials. Addressing the bottlenecks of growing large-size crystals with high optical quality and complex first-principles calculations in existing materials, this research is of great value for developing novel high-response electro-optic materials. Summary of the Invention

[0003] The purpose of this invention is to provide a growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic performance, aiming to solve the problems of difficulty in screening existing electro-optic crystals and limited electro-optic response.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic properties, comprising: Step 1: Weigh the raw materials according to the molar ratio Bi2O3:WO3=1:1, and synthesize Bi2WO6 powder using the solid-state method; Step two: The Bi2WO6 powder is pressed into sheet-like samples for infrared and Raman spectroscopy testing. Infrared oscillation intensity data is extracted from the infrared spectrum, and average Raman scattering efficiency data is extracted from the Raman spectrum. The contribution of ion motion is extracted based on peaks in the same wavelength band in the data. c l ; ; In the formula, n i and n j It is the principal axis refractive index of the crystal. e 0 is the vacuum dielectric tensor. f m It is the infrared oscillation intensity of the m-th vibration mode. s m It is the Raman scattering efficiency of the m-th vibrational mode. S Represents the Faust-Henry coefficient; The second harmonic generation (SHG) coefficient of Bi2WO6 powder was measured, and the electron motion contribution was extracted from the SHG coefficient measurement data. c e ; ; In the formula, n i and n j It is the principal axis refractive index of the crystal. d ijk It is the SHG coefficient.

[0005] Contribution of ion motion c l and electron motion contribution c e The electro-optic coefficient was finally calculated. c=c l +g e ; Step 3: Mix Bi2WO6 powder with co-solvent Li2WO4 and load it into a platinum crucible. Place the platinum crucible into a molten salt growth furnace and heat it to form a homogeneous melt. Step four: Set the cooling program, cool to room temperature and then anneal quickly to remove the flux, finally obtaining Bi2WO6 crystals.

[0006] In a preferred embodiment, in step one, the purity of both Bi2O3 and WO3 is 99.99% or higher.

[0007] In a preferred embodiment, in step two, Bi2WO6 powder is hot-pressed and sintered into a dense sheet sample using spark plasma sintering (SPS).

[0008] In a preferred embodiment, in step three, the Bi2WO6 powder and flux are placed in a ball mill for thorough grinding and mixing.

[0009] In a preferred embodiment, in step three, the molar ratio of Bi2WO6 powder to co-solvent Li2WO4 is 7:3.

[0010] In a preferred embodiment, in step three, the temperature is raised to 1000°C and held for 5 hours to form a uniform melt.

[0011] In a preferred embodiment, the cooling process in step four is as follows: first, the temperature is reduced to 900°C at a rate of 0.5-1°C / min, then reduced to 800°C at a rate of 3°C / min, and then allowed to cool naturally to room temperature.

[0012] In a preferred embodiment, in step four, the platinum crucible is soaked in hot nitric acid to remove the flux.

[0013] This invention utilizes Bi2WO6 powder to calculate the electro-optic coefficient, greatly reducing computational and experimental costs; the prepared Bi2WO6 electro-optic crystal material has a smooth, crack-free surface and a large calculated electro-optic coefficient.

[0014] Furthermore, the present invention has a simple process, high preparation efficiency, low cost, and a simple crystal growth process. Attached Figure Description

[0015] Figure 1 The images shown are the XRD pattern (a) and crystal image (b) of the Bi2WO6 electro-optic crystal material prepared in Example 1 of this invention. Figure 2 This is a spectral fitting data diagram of the Bi2WO6 electro-optic crystal material prepared in Example 1 of this invention; Figure 3 This is a graph showing the electro-optic coefficient data of the Bi2WO6 electro-optic crystal material prepared in Example 1 of this invention. Detailed Implementation

[0016] This invention provides a growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic performance, which uses the molten salt method to grow Bi2WO6 single crystals and innovatively proposes a spectroscopic-SHG joint testing strategy. This method can evaluate electro-optic performance without the need to prepare large-size single crystals, thus significantly reducing R&D costs.

[0017] Step 1: Weigh the raw materials according to the molar ratio Bi2O3:WO3=1:1 and synthesize Bi2WO6 powder using the solid-state method.

[0018] More specifically, the solid-phase method described above involves thoroughly grinding and mixing the raw material powder, sintering it in a muffle furnace, heating it to 800°C and holding it at that temperature for 72 hours, taking it out and grinding it multiple times during the process, and finally obtaining a yellow powder.

[0019] The purity of the above-mentioned raw materials, Bi2O3 and WO3, is 99.99% or higher. Since Bi2O3 is volatile at high temperatures, its dosage can be 5% mol in excess. The above raw materials are ground evenly, then ultrasonically cleaned with deionized water and anhydrous ethanol and quickly dried.

[0020] Step two: The Bi2WO6 powder is pressed into sheet-like samples for infrared and Raman spectroscopy testing, and the test data is fitted. Figure 2 Combining the formula, infrared oscillation intensity data is extracted from the infrared spectrum, and average Raman scattering efficiency data is extracted from the Raman spectrum. The contribution γ of ion motion is extracted based on peaks in the same wavelength band within the data. l ; ; In the formula, ni and n j It is the principal axis refractive index of the crystal. e 0 is the vacuum dielectric tensor. f m It is the infrared oscillation intensity of the m-th vibration mode. s m It is the Raman scattering efficiency of the m-th vibrational mode. S This represents the Faust-Henry coefficient.

[0021] The second harmonic generation (SHG) coefficient of Bi2WO6 powder was measured, and the electron motion contribution γ was extracted from the SHG coefficient measurement data using a formula. e ; ; In the formula, n i and n j It is the principal axis refractive index of the crystal. d ijk It is the SHG coefficient.

[0022] Contribution of ion motion c l and electron motion contribution c e The electro-optic coefficient was finally calculated. c ( Figure 3 ); ; When performing infrared and Raman spectroscopy tests, the dried sample is hot-pressed and sintered into a dense sheet-like sample using spark plasma sintering (SPS).

[0023] Step 3: Mix Bi2WO6 powder with co-solvent Li2WO4 and load it into a platinum crucible. Place the platinum crucible into a molten salt growth furnace and heat it to form a homogeneous melt.

[0024] The Bi2WO6 powder and flux are placed in a ball mill for thorough grinding and mixing to ensure that they can be melted uniformly.

[0025] The platinum crucible was placed in a molten salt growth furnace and heated to 1000°C. It was kept in a molten state for 5 hours to ensure that Li2WO4 was fully dissolved into the Bi2WO6 matrix.

[0026] Preferably, the molar ratio of Bi2WO6 powder to co-solvent Li2WO4 is 7:3.

[0027] Step four: Set the cooling program, cool to room temperature and then anneal quickly to remove the flux, finally obtaining yellow Bi2WO6 crystals.

[0028] The cooling procedure is as follows: First, cool to 900℃ at a rate of 0.5-1℃ / min. This cooling rate must be extremely slow; if the rate is too fast, it will cause severe cracks to form in the crystal. Then, cool to 800℃ at a rate of 3℃ / min, and then allow to cool naturally to room temperature.

[0029] After cooling to room temperature, the platinum crucible is soaked in hot nitric acid to remove the flux.

[0030] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art.

[0031] Example 1 Bi₂O₃ and WO₃, both with a purity of 99.99%, were weighed according to a molar ratio of Bi₂O₃:WO₃ = 1:1. The raw materials were ground evenly, then ultrasonically cleaned with deionized water and anhydrous ethanol, and rapidly dried. Bi₂WO₆ powder was synthesized using a solid-state method. The raw material powder was thoroughly ground and mixed, then sintered in a muffle furnace at 800℃ for 72 hours, with repeated grinding during the process, finally yielding a yellow powder.

[0032] The synthesized Bi₂WO₆ powder and the co-solvent Li₂WO₄ were weighed at a molar ratio of 7:3 and thoroughly ground and mixed in a ball mill. The mixture was then placed in a platinum crucible and placed in a molten salt growth furnace, heated to 1000°C, and kept in a homogeneous melt state for 5 hours.

[0033] The cooling program was then set up, first cooling to 900℃ at a rate of 0.5℃ / min, then cooling to 800℃ at a rate of 3℃ / min, and then allowing it to cool naturally to room temperature for rapid annealing. The platinum crucible was then immersed in hot nitric acid to remove the flux, finally yielding yellow crystals.

[0034] XRD analysis of the crystal confirmed the presence of high-quality Bi2WO6 single crystals grown along the b-direction (e.g., Figure 1 (As shown).

[0035] This embodiment uses Bi2WO6 powder to evaluate its electro-optical properties. Bi2WO6 powder was hot-pressed and sintered into dense sheet-like samples using spark plasma sintering (SPS) for infrared and Raman spectroscopy testing. Based on formulas, infrared oscillation intensity data was extracted from the infrared spectrum, and average Raman scattering efficiency data was extracted from the Raman spectrum. The contribution γ of ion motion was extracted from peaks in the same wavelength band within the data. l ; ; In the formula n i and n j It is the principal axis refractive index of the crystal. e 0 is the vacuum dielectric tensor. f m It is the infrared oscillation intensity of the m-th vibration mode. s m It is the Raman scattering efficiency of the m-th vibrational mode. S This represents the Faust-Henry coefficient.

[0036] The second harmonic generation (SHG) coefficient of Bi2WO6 powder was measured, and the electron motion contribution γ was extracted from the SHG coefficient measurement data using a formula. e； ; In the formula n i and n j It is the principal axis refractive index of the crystal. d ijk It is the SHG coefficient.

[0037] The electro-optic coefficient γ was finally calculated by combining the motion of ions and electrons. Figure 3 ); .

[0038] Example 2 The difference from Example 1 is that in the cooling process, the temperature was first lowered to 900°C at a rate of 1°C / min, then lowered to 800°C at a rate of 3°C / min, and then allowed to cool naturally to room temperature for rapid annealing. The platinum crucible was then immersed in hot nitric acid to remove the flux, finally yielding yellow crystals.

[0039] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A growth method for Bi2WO6 electro-optic crystal and an evaluation method for its electro-optic properties, characterized in that, include: Step 1: Weigh the raw materials according to the molar ratio Bi2O3:WO3=1:1, and synthesize Bi2WO6 powder using the solid-state method; Step two: The Bi2WO6 powder is pressed into sheet-like samples for infrared and Raman spectroscopy testing. Infrared oscillation intensity data is extracted from the infrared spectrum, and average Raman scattering efficiency data is extracted from the Raman spectrum. The contribution of ion motion is extracted based on peaks in the same wavelength band in the data. γ l ; ； In the formula, n i and n j It is the principal axis refractive index of the crystal. ε 0 is the vacuum dielectric tensor. f m It is the infrared oscillation intensity of the m-th vibration mode. σ m It is the Raman scattering efficiency of the m-th vibrational mode. S Represents the Faust-Henry coefficient; The second harmonic generation (SHG) coefficient of Bi2WO6 powder was measured, and the electron motion contribution was extracted from the SHG coefficient measurement data. γ e ; ； In the formula, n i and n j It is the principal axis refractive index of the crystal. d ijk It is the SHG coefficient; Contribution of ion motion γ l and electron motion contribution γ e The electro-optic coefficient was finally calculated. γ=γ l +γ e ; Step 3: Mix Bi2WO6 powder with co-solvent Li2WO4 and load it into a platinum crucible. Place the platinum crucible into a molten salt growth furnace and heat it to form a homogeneous melt. Step four: Set the cooling program, cool to room temperature and then anneal quickly to remove the flux, finally obtaining Bi2WO6 crystals.

2. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 1, characterized in that: In step one, the purity of both Bi2O3 and WO3 is 99.99% or higher.

3. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 1 or 2, characterized in that: In step two, Bi2WO6 powder is hot-pressed and sintered into a dense sheet sample using spark plasma sintering (SPS).

4. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 3, characterized in that: In step three, Bi2WO6 powder and flux are put into a ball mill for thorough grinding and mixing.

5. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 4, characterized in that: In step three, the molar ratio of Bi2WO6 powder to co-solvent Li2WO4 is 7:

3.

6. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 5, characterized in that: In step three, the temperature is raised to 1000℃ and held for 5 hours to form a homogeneous melt.

7. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 6, characterized in that: In step four, the cooling procedure is as follows: first, the temperature is reduced to 900°C at a rate of 0.5-1°C / min, then reduced to 800°C at a rate of 3°C / min, and then allowed to cool naturally to room temperature.

8. The growth method for Bi2WO6 electro-optic crystal and its electro-optic performance evaluation according to claim 1 or 7, characterized in that: In step four, the platinum crucible is soaked in hot nitric acid to remove the flux.

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